Researchers explore loosely overdamped system with extreme low stiffness for nanoparticle sorting with nanometer precision.

In this paper, low-frequency band-gaps (BGs) in a phononic crystal (PC) thin plate with periodic spiral resonators are investigated numerically and experimentally. The formation mechanisms of the BGs in the proposed structure are explained based on the modal analysis. We find that the interaction between the local resonances and the traveling wave modes in the plate is responsible for the formation of the BG in low-frequency range. This interaction strength greatly affects the bandwidth of the BG, of which the lower edge depends on the corresponding local resonance frequency. It is shown that the out-of-plane BG can be modulated by changing the geometrical parameters. The proposed PC plate is demonstrated to possess a broad out-of-plane BG in lowfrequency range from 42 Hz to 150 Hz, by combining the numerical calculations with experimental measurements. The structure design and its results provide an effective way for phononic crystals to obtain broad BGs in low-frequency range, which has potential applications in the low-frequency vibration and noise reduction. V

An optofluidic chip is demonstrated in experiments for high-resolution and multi-range particle separation through the optically-induced microscopic vibration effect, where nanoparticles are trapped in loosely overdamped optical potential wells created with combined optical and fluidic constraints. It is the first demonstration of separating single nanoparticles with diameters ranging from 60 to 100 nm with a resolution of 10 nm. Nanoparticles vibrate with an amplitude of 3-7 μm in the loosely overdamped potential wells in the microchannel. The proposed optofluidic device is capable of high-resolution particle separation at both nanoscale and microscale without reconfiguring the device. The separation of bacteria from other larger cells is accomplished using the same chip and operation conditions. The unique trapping mechanism and the superb performance in high-resolution and multi-range particle separation of the proposed optofluidic chip promise great potential for a diverse range of biomedical applications.

Many advanced physical properties can be realized by using well-designed acoustic metamaterial (AM) structures, which have significant application value in engineering. In particular, thin-walled membrane, plate, and shell-type structures with deep subwavelength thicknesses that can meet light weight requirements have attracted the attention of many researchers and engineers from various specialized fields. This Tutorial systematically introduced the structural design methods, acoustic/elastic wave attenuation and regulation principles, and engineering applications of thin-walled AMs for low-frequency sound insulation, sound absorption, and vibration reduction. In particular, the design methods and sound insulation/absorption properties of thin-walled AMs for realizing narrow-band and broadband sound attenuation were explored. Furthermore, the local resonance bandgap characteristics, quantitative extraction method for the bending wave bandgap, vibration suppression properties, and the design method for local resonance vibration dampers for elastic wave regulation by thin-walled elastic metamaterials were summarized successively. Moreover, other thin-walled AM applications, such as the wavefront steering performance of thin-walled acoustic/elastic metasurfaces, and the active thin-walled AMs, were introduced as well.